Most modern automotive vehicles include a variable valve timing mechanism in order to vary the opening and closing valve times of the exhaust and intake valves. Typically variable valve timing mechanisms include a lock pin that locks the variable valve timing mechanism during a shutdown of the internal combustion engine in preparation for the engine's next start. However, if the lock pin fails to properly engaged or disengage, the variable valve timing mechanism produces increased noise and vibrations during shutdown and startup procedures. The increase in noise and vibrations result in a decrease in customer satisfaction and affects the perception of quality of the engine.
With reference to FIGS. 5A-5C, a previously known lock pin 100 is provided with an insertion section 110 having a generally cylindrical shape. The insertion section 110 of FIGS. 5A and 5B provides reliable disengagement from the lock bore 112 as the linear outer side profile, as best seen in FIG. 5B, of the insertion section 110 prevents tilting of the lock pin 110 with respect to the lock bore 112. However, the linear outer side profile provides unreliable engagement of the lock pin 110 within the lock bore 112. As best seen in FIG. 5C, due to the similarities in the diameters of the insertion section 110 and the lock bore 112 minor misalignments prevent the reliable engagement of the lock pin 100 and the lock bore 112. In the event of a misalignment, the distal end 114 of the insertion section 110 abuts the will abut the edge of the lock bore 112 preventing engagement and causing increased noise and vibrations.
An alternative embodiment of the lock pin is disclosed in FIGS. 6A-6C a second previously known lock pin 200 includes an insertion section 210 having a tapered cylindrical shape. The tapered cylindrical shape of the insertion section 210 provides for the reliable engagement of the lock pin 200 within the lock bore 212 due to the insertion section 210 having a distal end 214 having a diameter smaller than the diameter of the lock bore 212. However, due to the linear outer side profile of the tapered cylindrical shape of the insertion section 210 the lock pin 200 is susceptible to sticking and jamming during disengagement. In the event that the lock pin 200 is tilted during disengagement, due to the misalignment of the lock pin with the lock bore 212, the linear outer side profile of the insertion section 210 becomes jammed due to a cinching effect with the lock bore 212. The resulting jam between the insertion section 210 and the lock bore 212 resulted in increased noise and vibrations of the variable valve timing mechanism.
Thus, there exists a need in the art to provide a locking pin which locks and unlocks easily without sticking so as to avoid additional noise and vibrations during engine shutdown and startup procedures.